To detect a position without causing microscopic displacement, by exciting a stepping motor, before detecting a position sensor, by repeating driving of a branch claw in a plurality of times.

The stepping motor is excited (S22) by a printing command (S21), and position sensor output is confirmed (S23). In "ON" (Yes of S23), the first branch claw is driven in the reverse rotation direction of turning off sensor output "ON" (S24), and when changing to "OFF from ON" in a predetermined time (Yes of S25), the first branch claw is driven in the normal rotation direction (S27). In "OFF" (No of S23), processing S27 is performed, and when changing to "ON from OFF" in the predetermined time (Yes of S28), rotation is stopped by excitation of the stepping motor (S29). When a change is not caused in the predetermined time in S25 and 28, S24 and 27 confirm whether or not to be in a predetermined frequency (S26 and 30), and in the predetermined frequency (Yes of S26 and 30), the processing is transferred to processing S23, and in the predetermined frequency or more (No of S26 and 30), abnormality is displayed on an operation part by stopping the stepping motor and a device body (S31, 32 and 33).